New drug makes brain tumors glow hot pink
CLEVELAND – An experimental drug that glows hot pink when illuminated with a special blue light from an operating microscope can identify the difference between tumors and healthy tissue, improving tumor resection and increasing patient survival rates.
Stage 4 glioblastoma, the most aggressive form of brain cancer, is the most difficult to treat because the tumor tissue looks and feels much like brain tissue. “It’s hard to figure out necessarily where tumor ends and swollen brain tissue begins,” said Dr. Andrew Sloan, director of the Brain Tumor and Neuro-Oncology Center and the Peter D. Cristal Chair in Neurosurgery at University Hospitals Case Medical Center.
Dr. Andrew Sloan uses a blue light to identify and remove tumor cells that glow hot pink with the experimental drug 5-ALA.
To help identify the difference between tumors and healthy tissue and to improve tumor resection, Sloan is testing an experimental drug called 5-Aminolevulinic Acid (5-ALA). The drug makes brain tumor cells glow hot pink when illuminated by a special blue light incorporated into his operating microscope. The technique makes it possible for surgeons to visualize the edges of a tumor more clearly so that they can remove it more completely from the brain.
Before – and during – the surgery, patients are given the experimental drug by mouth. Sloan then uses the blue light to identify and remove tumor cells through a process called fluorescent-guided resection (FGR).
Compared with normal tissue, high-grade gliomas metabolize 5-ALA to a fluorescent compound called protoporphyrin ix, a structure similar to that of chlorophyll found in plants. Tumors that absorb the compound fluoresce with the blue light. By using a specially modified surgical microscope that contains the blue light, Sloan can see the glowing tumor tissue and help guide it out of the brain.
An MRI of a brain with no tumor. Images courtesy of University Hospitals Case Medical Center.
We think that 5-ALA will help to improve the extent of resection in patients with malignant brain tumors,” Sloan said. “If we get out 95 to 99 percent of the tumor, we can almost essentially double the patient’s survival.”
5-ALA is routinely used for FGR procedures in Europe, but it has not yet been approved by the FDA for use in the US. Case Medical Center is one of only a handful of hospitals studying the drug in the US for brain tumor surgery. Sloan is working with Dr. David Dean, associate professor and director of the imaging laboratory in the Department of Neurological Surgery at Case Western Reserve University to determine the effects of varying 5-ALA dose levels. They hope to improve how FGR is performed by precisely measuring protoporphyrin ix fluorescence in tumors using a digital fiber optic probe during surgery, and they believe that the probe will be both more sensitive and more precise than the current technique, which is based on a surgeon’s perception of how “pink” the tumor is.
“Once we establish the optimal dose of 5-ALA to use for FGR, we would like to extend its use and see more sophisticated detection technology improve the use of this technology,” Sloan said.
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